Generally, wireless enabled devices have to pass a variety of industry and regulatory certifications before they can be put on the market. The certifications include regulatory/compliance testing such as electromagnetic compatibility (EMC), conformance testing such as protocol, radio frequency (RF), radio resource management (RRM) and location-based service (LBS), as well as performance testing such as over-the-air (OTA) measurements. OTA measurements are specifically performed to measure antenna patterns and include the measurement of the radiated transmit power (TRP) of a device under test at incremental locations surrounding the device. For performing such testing, the device under test (DUT) should be movable in a desired direction to allow accurate measurements within a short measurement time. In order to move the DUT a positioner using a motor as drive unit is usually provided.
Since motors generate unintended electromagnetic radiation that negatively affects measurement results, it is critical to provide an effective shielding between electromagnetic radiation caused by drive-motors and the DUT. Moreover, since a transmission equipment required for performance and conformance testing also generates unintended RF radiation such as unwanted spurious radiation, it is further desired to provide an effective shielding between the unintended RF radiation emitted by the transmission equipment and the DUT.
The document WO2017144079A1 relates to a method and a system for determining the level of out-of-band and spurious emissions generated by radio equipment. Such measurements are especially required for type approval or production line testing in order to satisfy electromagnetic interference (EMI) compliance tests and regulatory requirements, and to satisfy customer requirements. The cited document discloses a test system comprising transmission equipment that is configured to transmit a transmission signal including emissions in an in-band domain and emissions in an unwanted domain. The test system further comprises a measurement equipment and a frequency selective surface that is arranged between the transmission equipment and the measuring equipment to receive the transmission signal. The frequency selective surface attenuates the transmission signal in the in-band domain of the transmission signal but allows propagation of the transmission signal in the unwanted domain of the transmission signal. The aforementioned measurement equipment is configured to measure parameters of the transmission signal in the unwanted domain in order to determine the level of out-of-band and spurious emissions. Even though the cited document discloses a frequency selective surface between the transmission equipment and the measuring equipment to separate one overall signal in unwanted and wanted signals, however, the document does not teach an effective shielding of a DUT from unintended radiation emitted by a motor and/or a test antenna. The document is not at all related to the shielding of devices from unintended RF radiation.
The document US20140210502A1 is related to a method and apparatus for an enhanced reverberation chamber. The cited document discloses an apparatus including positioners connected to at least one motor, wherein devices involved with a test may be mounted to the positioners. In one embodiment, a measurement antenna is mounted on a first positioner and a calibration antenna to be tested is mounted on a second positioner. A line of sight (LOS) shield made of metallic material separates the first and second positioners. The LOS shield is used to block line of sight electric field components between the devices mounted on the two positioners. Disadvantageously, however, the metallic LOS shield reflects radio frequency (RF) radiation instead of absorbing it. The reflected radiation can interfere with other signals and falsify measurement results. Moreover, the cited document fails to recognize that a DUT has to be shielded from unintended radio frequency radiation emitted by a motor or a test antenna.
What is needed, therefore, is a measurement system for measurements of a device under test (DUT), which includes a shield for shielding the DUT from unintended radio frequency radiation emitted by a motor and/or a test antenna.